A mechanical dental probe is now used to diagnose periodontal disease. The probe comprises a stainless steel instrument shaped to slide between a tooth and the gum with the probe tip diameter being about 0.7 of a millimeter (mm). Depending on the particular prior art probe being used, reference marks may occur along the length of the probe at depths of 3, 6, 8 and 10 mm or 1, 2, 3, 6, 8, and 10 mm. Due to a variety of factors, pocket depths are not reproducibly determined to a precision better than 0.5 mm.
A healthy gum tissue is firm, has a coral pink color and fits tightly to the teeth. Healthy gum tissue does not bleed when brushed, flossed or probed. The depth registered on the measuring probe for healthy gum tissue will be between 1 and 3 mm. This depth is the distance from the top of the gum surface to the attachment of periodontal ligament at its position relative to the alveolar crest.
The characteristics of the various phases of the gum disease periodontitis are well known as is the specific use of the stainless steel measuring instrument used to mechanically determine the depth of the periodontal cavity. An inflamed gum condition is called gingivitis where the gum tissue bleeds easily during brushing, flossing or probing and is characterized by being swollen, is red to purple in color and flaccid. The depth registered on the prior art measuring probe is still 1 to 3 mm.
In an early stage of periodontitis, the gum tissue condition is characterized by inflammation, loss of gum attachment and loss of bone support. The periodontal pocket depth is 3 to 5 mm with this early stage of periodontitis.
Finally, there is a moderate to advanced periodontitis condition in which the supporting gum and bone tissue have deteriorated and the tooth loosens. The periodontal cavity depth is 5 to 7 mm in moderate cases and greater than 7 mm in advanced cases. The free gingival margin may display a return to healthy appearance in these more advanced cases despite the continued bone loss.
With the prior art mechanical probe, a first set of measurements requires six measurements on each tooth, namely, one in each outer corner, one at the outer surface center, and a similar set on the inside outer surface of the tooth. For a patient with a full complement of 32 teeth, this requires 192 measurements. The dentist or technician may try to slide the probe along the outer surface of the tooth from one location to another without withdrawing the probe unless the patient complains about the discomfort. Each depth measurement must be recorded on an appropriate data sheet. Therefore, two people may be required to facilitate the taking of a set of measurements over the shortest time possible, i.e., one to make the measurements and the other to record them. Such a procedure may take up to about 20 minutes for each patient if properly performed.
Although ultrasound techniques have been used in medicine for years in the fields of obstetrics and ophthalmology, no viable ultrasound instrument exists for dental diagnostic purposes. Diagnostic ultrasound commonly uses the pulse echo technique for measuring distances. The reflected sound pulses are referred to as pulse echoes that return to the transducer where they are converted into electrical pulses which are displayed on a cathode ray tube as found in an oscilloscope.
Earlier attempts to use ultrasound pulses for measuring the depth of the periodontal pocket have failed. Therefore no ultrasonic procedure is available for replacing the often painful use of the mechanical measuring probe as described above. The earlier attempts at the use of ultrasound pulses to measure the periodontal cavity are described in an article entitled "The Use of Ultrasound for the Determination of Periodontal Bone Morphology" and found in the Apr., 1987 issue of J. PERIODONTAL. Page 262.
In accordance with the known ultrasonic procedure, an electrical pulse generator directs an electrical pulse to a transducer which changes the electrical pulse into a sound pulse. The transducer, in turn, directs the ultrasonic pulse to any desired surface where a pulse echo is reflected back to the transducer. The ultrasonic pulse echo is converted by the transducer to an electrical pulse for display on a cathode ray tube. The use of this technique, by itself, in the earlier ultrasonic periodontal diagnosing apparatus was found unsuccessful because the results were not accurately reproduced when compared to corresponding mechanical probe measurements.
It is difficult for one person to make a set of measurements along each tooth in a mouth for the purpose of diagnosing or tracking periodontal disease. As now practiced, the mechanical probe must be placed between the gum and the tooth, the measurement read along the edge of that probe followed by the recording of the reading. If one person is to do this, the probe must be removed from the mouth and placed down. A writing instrument then must be picked up and used. The same procedure must be repeated for each measurement. If a patient has a full complement of 32 teeth with six measurements for each tooth, this involves a full complement of 192 measurements, more than both the patient and the dentist could bear. Therefore, under normal circumstances, a technician records the readings called out by the dentist.